Capacitive rotatable coupler



y 1, 1952 R. J. ADAMS ETAL 2,602,118

CAPACITIVE ROTATABLE COUPLER Filed Aug. 8, 1945 gwoe/wtow ROBERT J.ADAMS LEE R. DOBLER Patented July 1,1952

"2,602,118 I "c raorr1vERo'r 'rABtE coUPLaaJ 3 'i that .1; ActinWashington, no and Iiee Ra: Dohler, United States Navy I 1ApplicationrAug ust 8, 1945, Serial No. 609,692,.-

scams; (01. 178- 14) I (firantedfunder the act of March. 3; 1883, as wamended April" 30, 1928; 3'70 0. G.--757)P This invention relates to arotatable coupler for the transmisson of alternating current between twotransmission lines rotating with respect toone. another, andis.particularly directed to the capacitive type'of. such rotatablecou'pler.

Rotatable couplers. which. aroused to couple one transmission line to asecond transmission line which: is connected" to; aiotatingl antennacommonly employ inductive gcoupling, which re 7 sults in rather sharptuning and considerable restriction on the width of; theifrequency bandpassed. The frequency lbandi passed by ar ma able coupler employingcapacitive coupling. is markedly broadenfthan that passed? by. a. rotatable couplerof the inductive}. typ'elfl r Furthermore, acapacitive/rotatable coupler may be constructed with a "diameterrelatively small or quite large, as; is desired, whereas the diameter ofthe inductive type coupler is fixed within rather narrow limits by thefrequency of the v lta e tobe passed, inaetheloop type cou pler must'notbemore than about oneequarter wave: length circumference; ;='Th6-capacitive type coupler thus allow swmore" flexibilityin design than theinductive=;type. i

It is accordingly: one obj ect of: this invention to provide arotatablecouplenforsooupling two transmission lines, which; will j pass;radio frequency energy over arelativelyawide'band of frequencies. y I jvQ r It is another object; ofe'the. invention-to provide sucharotatableocouplerwhich isstrong mechanically and ofsimple construction.

It is also an object of this z'mventionrtoprovide a, capacitiverotatable coupler for: coupling a transmission line toa rotatingantenna,;which coupler may-have a large enough internal diameterthat itmay bepositionedaround an antenna mount of relatively large externaldiameter;

It is another object of this invention to provide a capacitive rotatablecoupler whose transmission characteristics will not vary greatly withthe relative rotation of the upper element with respect to theilowerelementofithe; coupler.

In the accor'npanying. drawings: a a

Figure: 1 a diagrammaticrrepresentation of one embodiment orthis'inventiom-and 1 Figure 2is asection viewer-an embodiment: c thisinvention showingcertain structural details thereof.

In. the embodiment: of this invention; shown in Figure 1 concentricannulari conducting plates I andv 2', fixed with respect to" eachother,are similar in shape and difnens-ions to plates; 3; and I", which arealso fixediwithrespecttto each other.

The distance" between the first: andr second pairs or of plates'isexaggerated inthe drawing; the'plates are in practice separated.byonlya. ,smalldistance; for example,'one-eighthzofan inch-l Thesefour'platesi are positionedcoaxially sothat plates I and 2'rotatezwithres'pectto platesft'v and: 4 about their'common axis.

Adequate means" of insulation'and support of the plates can be developed:for-any set of requirements, as this invention permits of considerableflexibility in choice; of the j dimensions of the plates; employed inanembodiment suchasris illustrated in: Figure 1 "which Was-designed t0?surroundi a rotating antenna mount having anrexternalz die ameterofisomewhat less-.than twelve-inches: external diameter of; rings I--and: 3+20-inches, internal diameter .of; rings I: and 3-1:7 inches,external diameter of rings" 2 and lie-16' inches, and internal diameterof ringsZ and l-h-l-zvinches. This. embodiment was usedwithgoodiresultsto pass a frequency .--band of'abOutlO-rp'er cent-in theneighborhoodaof-200'mc,/s.

In the; embodiment, of1F'igure; .1; the capacitive rotatable couplerservesnto' couple; unbalanced transmission line=5with unbalanced,transmission line 6.. Transmission line'5 feeds line-balance converter"1, while transmission line 6 feedslinebalance converter 8;

From line-balance; converter 1* three parallel wire transmission lines II, 12- and. t3: lead-to plates l and 2; One wire. of. each oftransmission lines ll, [2 and l-3zisconnected to plate I atfeed points120 apart-from each other; while the other wire of each-of thesethreetransmission lines. is connected to plate: 2 at feed points-:ha-vingsubstantially the same radial positions as of these "two transmission:lines is-Jconnectedto plate. 4 at feed pointshaving substantially thesame radialpositions aswthe pointsrof connection-for plate 3; The feed.points foranyone of transmissionw'lines H: through I willhereinafter bereferred to as pairs of feed DOiljltSxiEOl.

the. respectiveplates: I e

- Inrtheoperationi-of thisinvention,alternating voltages may be appliedion either ,side ofxthe rotatable 'couplerzand alternating current willv betransmitted through the coupler. If'an. alternetting voltage: isappliedito one wire of each; of parallel wire transmissionilines ll,f|:2 an

-f r x mpl With an alternating voltage-"oili The following dimensions:wereverse phase applied to the other wire of each of these threetransmission lines, these alternating voltages will appear on capacitorplates l and 2. Alternating voltages of exactly the opposite phase willbe inducedon the other capacitor plates 3 and v4, respectively, and willthus be impressed on transmission lines l4 and I5, causing alternatingcurrent to flow therein. Since the capacitor comprised of plates 1 and 3and the capacitor comprised of plates 2 and 4 are of large capacitance,the capacitive reactance presented by this rotatable coupler tothetransmission of alternating current is very small.

It will be seen that as plates I and 2 rotate with respect to plates 3and 4, at no time is more than one pair of feed points for plates l and2 shown and described is exemplary only, and that the scope of theinvention will be determined with reference to the appended claims.

The invention described herein may be manufactured, and used by orfor.the Goyernment of the United States of America for governmentalpurposes without payment of any royalties thereon or therefor.

aligned radially with a pair of feed points for plates 3 and 4. If atany instant one pair of feed points for plates 1 and 2, say at thetermination of transmissionline H, has'the same bearing as apair of feedpoints for plates 3 and 4, say at the termination'of transmissionline"l4, then at this invention presents to alternating current of agiven frequency an impedance which remains reasonably fiat, without anysharp peaks, as plates I and 2 are rotated through 360 withrespect toplates 3 and 4.

The number of parallel wire transmission lines feeding the upper andlower pairs of plates may be varied as desired and the flat impedancewith relative rotation of the two'halves of the coupler will beretained, if the number of transmission lines feeding one pair of platesis neither a factor nor an integral multiple ofthe'number oftransmission lines feeding the other pair of plates. For, if thisnumerical relationship is maintained, then at no time will more'than onepair of feed points for plates l and 2 be aligned radially with a pairof feed points for plates 3 and 4. V

Figure 2 shows in section how plates l and 2 may be rotatably mountedwith respect to plates 3 and 4. Shaft 20 maybe, for example, an antennapedestal supporting rotatably thereon shaft 2 I, journaled in bearing 22of shaft 20. Attached to shaft 20 is an annular plate 23, and attachedto shaft 2| is annular plate 24. Plate l is attached to plate 24 by anumber of insulators 25, and plate 2 is also attached to plate 24 by anumber of insulators 26. In the same way plates'3 and 4 are attached toplate 23 through insulators 21 and 28, respectively; It will be seenthat plates 1 and 2 will rotate with respect to plates 3 and 4 as shaft2|, supporting an antenna, for example, rotates with respect to shaft20.

It will be understood that because of the width of the annular plates[through 4 slight lateral displacements of any of those plates will notresult in'undue variations in the transmission characteristics of thisrotatable coupler as transmission line 5 rotates'with' respect totransmission line 6.

In casethis invention is to be employed in coupling twobalancedtransmission lines, the embodiment of Figure l'may of course be modifiedby elimination of line-balance converters I and 8. The operation of sucha rotatable coupler would be in all other respects similar to that o theembodiment of Figure 1.

It will be understood that the embodiment What is claimed is:

l. A rotatable coupler for the transmission of alternating electriccurrent between two balanced transmission lines rotating with respect toeach other comprising two coaxial annular conductin plates flxedwithrespect to each other, a number of m of parallel wire transmission linesfeeding said two plates, one wire of each of said "122.transmissionlines being connected to one of said plates at points spacedsubstantially degrees from each other and the other wire of each of saidm transmission lines being con two plates at connection points spaced a7 degrees from each other,'the'number "n being any number neither afactor nor an integral multiple of said number m, said "12. parallelwire transmission lines being-fed in parallel bythe other of said twobalanced transmission lines, the second pair of plates being positionedcoaxially with thefirst pair and'sepa'ratedby a small distance from said'fir'st' pair, and means for rotatably mounting one of said pairs ofplates with respect to the other of said pairs of plates.

2. A rotatable coupler for the transmission of alternating electriccurrent between two unbalanced transmission lines rotating with respectto eachother comprising two coaxial annularconducting plates fixed withrespect to each'other, a number "m of parallel wire transmission linesfeeding said two plates, one wire of eachof said 111. transmission linesbeing connected to one of said plates at points spaced substantiallynected to the other of said plates at points having substantially thesame radial positionsgas the corresponding points .of connection on saidone plate, a line-balance converter feeding said fm transmission linesin parallel and being .fed by one of said two unbalanced transmissionlines, third and fourth coaxial annular conducting plates fixed withrespect to eachother and of substantially the same lateral dimensions asthe first two plates. a; number n of parallel wire transmission linesfeeding said third and fourth ing plates,- a plurality of connectionsbetween each conductor of said first'line andadifferent one of saidconducting plates at various'angular points around the circumference ofsaid plates, a second pair of coaxially disposed annular conductingplates ofsimilar dimension located in close proximity to the first pairand rotatable with respect thereto, and a connection between eachconductor of the second line and the respective plates of the secondpair at various angular positions around the circumference thereof, theconnections to thes'econdpair of plates having a difierent angularrelationship than those to the first pair of plates. I Q

8. A rotatable 'couplerfor the transmission of alternating currentbetween a first transmission line and a second transmission line whichis rotatable relative to said first transmission line comprising a firstset of coaxially disposed annular conducting plates, one for eachconductor of the first line, a plurality of connections betweeneachconductor of the first line and a difierent one of said conductingplates at various angular points around the circumference of the plates,a second set of coaxiallyf disposed annular conducting plates, ofsimilar dimension and located inclose proximity to the said first set ofplates, and rotatable with respect thereto, one. for each conductor ofthe second line, a connection between each conductor of the second lineand a respective conducting plate of said second set of plates atvarious angular points around the circumference of the plates theconnections to said second set of. plates having a different angularrelationship than those to said first set of plates. v

9. In a rotary coupler system wherein-energy is coupled between twotransmission line systems through a first and second set of-respectively capacitively coupled, coaxially I related plates where oneof the plates of'ea'ch set are simultaneously rotatable with respect tothe associated plate of each set, and where the impedance variationsbetween the said-sets of plates varies appreciably with rotation of therotatable plates thereof, the improvement comprising m transmissionlines connectedin parallel'tooneef said .two transmission line systems;means connecting each set of commonly connected conductors,saidtransmission lines respectively to a different rotatable plate ofsaid sets of plates, the commonly. connectedconductors connecting to theassociatedplate at different points thereon surrounding the axis ofrotation thereof, fin transmission lines connected in parallel to theother one of said transmission line systems, means connecting the setsof commonly connected. conductors of said latter transmission linesrespectively, to, a different one of the other plates of said respectivesets of plates, the commonly connected conductors connecting to theassociated plate at'different points about the axis of rotation, of theassociated rotatable plate, the number n being neither a factor nor aninteger of said number ("1") ROBERT J. ADAMS. LEE R. DOBLER.

REFERENCES CITED The following references are of record in the file ofthis patentnf UNITED STATES PATE TS-

